Once you've written down your transition with a fact or detail, you should include an explanation to go with the fact (more
than one explanation is OK).
example: They (dolphins) must come to the surface of the water to breathe and get oxygen from the air. However, unlike
mammals, fish can take oxygen from the water.
In this example, the author explains that because the dolphin has lungs it needs to come to the surface to breathe. This
explains the fact that dolphins have lungs.
The second sentence explains even further that dolphins aren't fish because they can't breathe in the water.